Multiple furnace



. y 1935- c. l. HAYES 2,000,664

Original Filed Oct. 2, 1929 2 Sheets-Sheet 1 V r% V INVENTOR.

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Patented May 7, 1935 MULTIPLE FURNACE Carl I. Hayes, Cranston, R. I., assignor to Harold C.Field, Providence, It. I.

Applicationoctober 2, 1929, Serial No. 396,716

-, Renewed April 25, 1932 15- Claims. (01. 263-36) My present inventionrelates to heat treating, and has particular reference to a method and an apparatus suitable for the multiple heat treatment. of metals. r

One object of my invention is to provide a novel method of: multiple heat treatment under controlled atmospheric conditions.

Another object is to provide a novel apparatus for multiple heat treatment which permits the sequence of treatments to be carried'out without exposure of the treated material to the surrounding atmosphere. W

A further object is to provide an-rimproved apparatus which simplifies multiple ,heat treatment while facilitating the continuousinspection and supervision-of the treated material 7 An additional object is to provide an: improved apparatus for heat treatment, including a.plu rality of chambers which are maintained unde predetermined atmospheric conditions; Still another object is to provide an improved apparatus comprising a plurality of chambers each of which may have individually controlled atmospheric conditions therein. 1

These and other objects and advantageous features will be readily apparent from'and will be more fully described in the detailed description following, in conjunction with the .accompanying drawings, and will be particularly pointed out in the appended claims:

' In the drawings: p l r Fig. 1 is a perspective view-of the novel multiple furnace; r v

Fig. 2 is a centralhorizontal section of Fig ure 1;

- ig. 3- is a verticalsection on the line 33 Fig. 4 is a section similar-to Figure 2, showing individual combustion chambers and nozzle slots for the individual furnaces.

The multiple heat treatment, of, high speed steels and the like has usually included a preliminary heat treatmentat a relatively low temperature, and a high temperature heat treatment followed by quenching in oil or the like. These steps, and similar further steps when required, have heretofore been carried out indifferent furnace chambe'ranecessitating transfer of the treated material through the surrounding atmosphere and resultant oxidation. I have devised a novel method and apparatus for multiple heat treatment, which utilizes separate furnace chambers for each step, the chambers communicating with each other to permit free transfer of the material to be treated, and the atmospheric conditions in each chamber and in the communicating passageways being positively controlledto exclude outside atmospheric air and to maintain an enveloping, atmosphere for the treated; ma-

terial of a predetermined constituency; and the 1 following is a detailedvdescriptionof-a specific arrangement which embodies'the principles of my invention; 1 j I Referring to the drawings, the multiple furnace l0 includes a preliminary heat furnace, I I, a-high i temperature furnace l2, and an enclosed passage way l3 which joins the two furnaces and forms an intermediate chamber communicating the throats l4 and I5 of the furnace chambers.

Each furnace chamber, as shown in Figure 3, ;.--1

ing tank 2 l=equipped withthe usual work receiving baskets 22. The tankZl extends ;out below the passageway l3, as shown in Figure 1, to b readily accessible to the operator. I The passageway l3 has a door, or entrance opening 23 "at the front thereof, the floor of theEopening having a narrow longitudinal nozzle slot 2-l 'of the type disclosed in Patent No. 1,724,583,

granted August 13, 1929. This nozzle slotreceiveslcombusted gases from a combustion chamber' 25, which is supplied with combustible gas and air or oxygen through the supply pipes 26, 21 respectively, the quantities of each being regulatedby a hand controlled valve, not-shown. I

The operation of my improved multiple heat treatment furnace maybe briefly described with specific application'to the multiple heat treatment ofalloy steel. The alloyv steel is first inserted into the preliminary heating furnace H, where the temperature of-the metal israisedto about '1600 degrees F. to impart an evenheat thereto. The operator now reaches intothe fur-, nace ll, through the entrance opening 23,'removes the heated metal and transfers it to the high temperature furnace I2, where it is heated to approximately 2350 degrees F.; as soonas'the proper high temperaturehas been reached, the operator removes the highly heated metal from furnace l2 and drops the same into the oil in quenching tank 2|, this oil being preferably maintained at approximately 300 degrees F. These successive operations are carried out in a controlled atmosphere by directing combusted gases from the combustion chamber 25 upwardly through the nozzle slot 24 to effectively curtain the opening 23, the combusted gases impacting on the roof of the opening 23 to enter and fill the furnaces I l and I2 and the passageway l3, as disclosed in Patent No. 1,724,583. The combusted gases are colorless, are transparent, do not inter fere in any way with the movements 'of the operators in transferring treated metal from one furnace to the other or to the quenching tank, effectively exclude all atmospheric air from contact with the metal during the treatment and the movements thereof, and fill the furnace chambers and the passageway with an enveloping atmosphere of predetermined constituency. In the case of high speed steel, it is found desirable to maintain a'slight excess of carbon monoxide in the enveloping atmosphere, which condition is readily obtained by suitable inspection means, for example, by observing a charcoal block indicator positioned in the high temperature furnace; as soon as the proportions of air and gases supplied to the combustion chamber insure com plete combustion, the charcoal, which glows brightly whenever any oxygen is present, immediately becomes extinguished. The heat treatment may be continuous for successive batches of material to be heated, since the basket 22 in the quenching tank may be repeatedly emptied without disturbing the atmosphericair exclusion.

Under certain circumstances, it may be preferable to position additional nozzle slots in the throats l4 and I5, such as indicated in Figure 4, the additional slots being connected to the combustion chamber by meansof valve controlled supply pipes (not shown) or individual combustion chamber slots and supply pipes may be installed for each furnace, as shown in Figure '4', thus obtaining either common or individual control of the enveloping atmosphere of the furnaces as desired. In addition, whenever very exact control of the constituency of the enveloping atmosphere in the high temperature or other furnace chamber is desired, a short outlet tube of standard construction (not shown) having a pet cock therein may be run through the roof of the high temperature furnace, to permit periodic withdrawal of samples of the atmosphere therein, for testing purposesl r -It will be noted that the use of a curtain of combusted gases is an-advantageous feature for heating furnaces, since there is no rapid movement of gases in the furnace chamber, no intro duction of gases at very different temperatures; the impacting of the combusted gases on the roof of the entrance opening produces a slow circulation of the enveloping atmosphere in the chamber without disturbing the heat distribution or the uniformity of heating therein.

Other changes in the structure and in the arrangement of the various furnaces, or in the procedure followed, may obviously be made to meet the requirements for heat treatment'ofspeciflc materials, Without departing from the spirit and scope of the invention as defined in the appended claims. 7

1. In combination, a furnace chamber for'preliminary heat treatment having a throat and otherwise closed, a furnace chamber for final heat treatment having a throat, and otherwise closed, a passageway communicating said throats and having an entrance opening and otherwise closed, and means for maintaining atmospheres of regulated constituency in said chambers and passageway.

2. In combination, a furnace chamber for preliminary heat, treatment having a throat and otherwise closed, a furnace chamber for high temperature heat treatment having a throat and otherwise closed, a passageway communicating said throats having an entrance opening and otherwise closed, a combustion chamber, and

means for supplying products of combustion from said combustion'chamber to form an atmosphere excluding curtain for said passageway opening.

3. In combination, a furnace chamber for preliminary heat treatment having a throat and otherwise. closed, a furnace chamber for high temperature heat treatment having a throat and otherwise closed, a passageway communicating said throats having an entrance opening and otherwise-closed, a combustion chamber, means for supplying products of combustion from said combustion chamber. to form an atmosphere exeluding curtain for said passageway opening, and means'for diverting said curtain gases into said passageway to fill said passageway and said furnace chambers. 1

4. In combination, a furnace chamber for preliminary heat treatment having a throat and otherwise closed, a furnace chamber for'final heat treatment having a throat and otherwisefclosed, a passageway communicating said throats and having an entrance opening, a quenching tank opening in the floor of said passageway, and means for excluding atmospheric air from. said furnacechambers and passageway.

5. In combination, a furnace chamber for preliminary heattreatment having a throat and other-wise closed, a furnace chamber for final heat treatment having a throat and otherwise closed, a passageway communicating said throats and. having an entrance opening, a quenching tank opening in the floor of said passageway, and means for maintaining atmospheres of regulated constituency in said furnace chambers and passageway.

6. In combination, a furnace chamber for preliminary heat treatment having a throat and otherwise closed, a furnace chamber for final heat treatment having a throat and otherwise closed, a passageway communicating said throats and having an entrance opening, a quenching tank opening in the floor of said passageway, a combustion chamber, and means for supplying products of combustion from said combustion chamber to form an atmosphere excluding curtain for said passageway opening.

7. In combination, a furnace chamber for preliminary heat treatment having a throat and otherwise closed, a furnace chamber for final heat treatment having a throat and otherwise closed, a passageway communicating said throats and having an entrance opening, a quenching tank opening in the floor of said passageway, a combustion chamber, means for supplying products of combustion from said combustion chamber to form an atmosphere excluding curtain for said passageway opening, and means for diverting said curtain gasesinto said passageway to fill said passageway and said furnace chambers.

' 8. In combination, a furnace chamber for preliminary heat treatment having a throat. a furnace chamber for high temperature heat treatment having a throat, a passageway communicating said throats having an entrance opening, a combustion chamber, and means for supplying products of combustion from said combustion chamber to form an atmosphere excluding curtain for said passageway opening.

9. In combination, a furnace chamber for preliminary heat treatment having a throat, a furnace chamber for high temperature heat treatment having a throat, a'passageway communicating said throats having an entrance opening, a combustion chamber, means for supplying products of combustion from said combustion chamber to form an atmosphere excluding curtain for said passageway opening, and means for diverting said curtain gas into said passageway to fill said passageway and said furnace chambers.

10. In combination, a furnace chamber for preliminary heat treatment having a throat, a furnace chamber for final heat treatment having a throat, a passagewaycommunicating said throats and having an entrance opening, a quenching tank opening in the floor of said passageway, and means for excluding atmospheric air from said furnace chambers and passageway.

11. In combination, a furnace chamber for preliminary heat treatment having a throat, a furnace chamber for final heat treatment having a throat, a passageway communicating said throats and having an entrance opening, a quenching tank opening in the floor of said passageway, a combustion chamber, and means for supplying products of combustion from said combustion chamber to form an atmosphere exeluding curtain for said passageway opening.

12. In combination, two furnace chambers for heat treatmenthaving entrance throats, a passageway communicating said throats and having an entrance opening, and means for maintaining atmospheres of regulated constituency in said chambers and passageway.

13. In combination, two furnace chambers for heat treatment having entrance throats, a passageway communicating said throats and having an entrance opening, and means for maintaining an atmosphere of regulated constituency in each chamber and in the passageway.

14. In combination, two furnace chambers for heat treatment having entrance throats, a passageway communicating said throats and having an entrance opening, means for supplying products of combustion, and means for conveying products of combustion from said supply means to form atmosphere excluding curtains for said entrance throats and said entrance opening.

15. In combination, two furnace chambers for heat treatment having entrance throats, a passageway communicating said throats and having an entrance opening, means for supplying 

